Heather Archuletta isn't an astronaut. But if the U.S. space program ever lands on Mars, she's taking partial credit.

A three-time participant in NASA's bed rest studies, Archuletta gives up weeks of her life for research on how space travel affects astronauts' bones, muscles and blood. In 2008, Archuletta, 40, an IT professional from Texas, was one of six people paid $160 a day to participate in a 90-day microgravity bed rest study. By remaining in bed for weeks at a time, the participants simulate gravity on a space station. (The research was halted at 50 days because Hurricane Ike forced the evacuation of Galveston, where the research was conducted.)

NASA continues to recruit new study participants. Archuletta, who hopes to join another study this spring, spoke with me yesterday about the bed rest research -- and why she thinks it's more important than ever.

In the microgravity study, you had to lie in bed tilted six degrees back. What effect did that have on your body?

The first couple days you lie there going, "What did I get myself into?" But I'm a huge space enthusiast and it was a dream come true for me to be at NASA, so I stuck with it. They assured me that everything you're going through is what astronauts go through, so that's what kept me going. You get changes in blood pressure, heart rate and even the fillings in my molars were throbbing. It's such a change to the body.

What was a typical day like during that study?

We get up at 6 o'clock everyday. They play music through our speakers just like they do at a space station. We are weighed every morning on an industrial scale. They make very, very specific amounts of food and water for you, so you stay at your target weight. There are times when you have to report to tests. People come in and wheel you into different rooms. They were taking 3-D sonograms of my heart and testing my muscle strength.

You're not allowed to nap during the day. You have to stay active. Everybody has their own television. I wanted to learn sign language, so I got books on American Sign Language and watched signing videos. I'm a big reader, too. I tore through 30 books. There's a common room where everybody can join for meals and do arts and crafts and watch movies together.

You use a bedpan. They have a special shower with a mesh gurney that you can roll onto because you have to bathe at [an angle of] negative six degrees.

How long did it take you to recover?

It was like someone was shoving knives into my feet [when I first tried to walk]. An ambulance took us to a hospital in Austin to recuperate. They had a physical therapist travel up there with us and he helped us with stretches and special exercises everyday. You'd walk for a little while, but then use a wheelchair for an hour. It was about a month before I was getting back into my own exerciseroutine. It took about two weeks until I could drive a car again.

What are the risks involved in these bed rest studies?

You'll have changes in the blood. You may have lowered bone density. Your muscles will certainly change. It was not an easy choice to make. I had a few moments of thinking, "I've only got one body and if anything really happens to me, what if it's not reversible?"

Knowing the risks and with the misgivings you had, what finally motivated you to participate?

Mars. I so want to see us land on Mars in our lifetime. And we've got the technology to do it. We've got the propulsion technology; we've got the spacecraft technology. The last piece of the puzzle is the human factor. We've gotten robots there; we can get a craft there. The bigger question is, "Can we get a human there healthy enough to collect rocks once he lands?" And if that ever does happen, I'm so proud that I'll be able to say I was a tiny little part of that.

Yes. Now more than ever. We can't stop being visionary because we don't have the money right now. Whether we go to Mars in 10 years or we go to Mars in 100 years, what we're learning now on the space station and what we're learning now in these studies will still be relevant when we reach Mars or a Mars moon or an asteroid. I think it's just going to be further in the future than we had hoped.